Enhanced exciton-phonon interactions in photoluminescence of ZnO nanopencils

We report enhanced exciton-phonon interactions in the photoluminescence (PL) of ZnO nanopencils compared with ZnO nanorods grown on ZnO/Si templates by thermal evaporation. Although the low temperature (<100 K) PL spectra of ZnO nanorods and nanopencils were dominated by the strong donor-bound exciton, the PL spectra at elevated temperatures (>100 K) showed dominant contributions from the free exciton emissions and phonon-replicas of free excitons for nanorods and nanopencils, respectively. This discrepancy in the behaviors of excitonic emissions of the ZnO nanorods and nanopencils was related to surface defects causing different strengths of exciton-phonon coupling. The different excitonic emissions of the nanorods and nanopencils revealed a 52 meV redshift in the room temperature PL of nanopencils.